中国及邻近陆域海域地球内部三维结构及动力学研究   总被引：27，自引：3，他引：24  

朱介寿  曹家敏  蔡学林  严忠琼 《地球科学进展》2003,18(4):497-503

根据国内外最新地球物理和其它地学资料,采用多学科多手段进行综合反演,建立中国及邻区高分辨率地球三维结构模型,为地学各领域提供高精度多参数地球三维模型数据库。对中国及邻近陆域海域岩石圈软流圈结构,过渡带以下直至核幔边界的地幔速度三维分布进行研究。探讨东亚及西太平洋边缘海板块运动、地幔对流、圈层耦合及物质运移等深部动力学问题。对中国大陆及边缘海各地块的结构及相互作用,特别是有关中国东部及边缘海岩石圈拉张减薄、西部岩石圈汇聚增厚的深部动力学过程作了探讨。  相似文献   

Green＇s functions for uniformly distributed loads acting on an inclined line in a poroelastic layered site   总被引：2，自引：1，他引：1  

梁建文  尤红兵 《地震工程与工程振动(英文版)》2005,4(2):233-241

Based on one type of practical Biot＇s equation and the dynamic-stiffness matrices ofa poroelastic soil layer and half-space, Green＇s functions were derived for unitformly distributed loads acting on an inclined line in a poroelastie layered site. This analysis overcomes significant problems in wave scattering due to local soil conditions and dynamic soil-structure interaction. The Green＇s functions can be reduced to the case of an elastic layered site developed by Wolf in 1985. Parametric studies are then carried out through two example problems.  相似文献   

On the Use of Changes in Dihedral Angle to Decode Late-stage Textural Evolution in Cumulates   总被引：9，自引：7，他引：2  

HOLNESS  MARIAN B.; CHEADLE  MICHAEL J.; McKENZIE  DAN 《Journal of Petrology》2005,46(8):1565-1583

The melt-filled pore structure in the final stages of solidificationof cumulates must lie somewhere between the two end-membersof impingement (in which pore topology is controlled entirelyby the juxtaposition of growth faces of adjacent grains) andtextural equilibrium (in which pore topology is controlled bythe minimization of internal energies). The exact position betweenthese two end-members is controlled by the relative rates ofcrystal growth and textural equilibration. For samples in whichgrowth has stopped, or is very slow, textural equilibrium willprevail. A close examination of dihedral angles in natural examplesdemonstrates that these two end-member textures can be distinguished.The impingement end-member results in a population of apparentsolid–melt dihedral angles with a median of 60° anda standard deviation of 25–30°, whereas the texturallyequilibrated end-member population has a median of 28° anda standard deviation of 14°. For the specific case of cumulatesin the Rum Layered Intrusion, residual porosity in troctoliticcumulates was close to the impingement end-member, whereas thatin peridotites was close to melt-bearing textural equilibrium.Suites of glass-bearing samples from small, or frequently disturbed,magma systems show modification of initial impingement textures.These modifications may be a consequence of textural equilibrationor of diffusion-limited growth during quenching. Distinctioncan be made between these two processes by a consideration ofgrain shape. The geometry of interstitial phases in suites offully solidified cumulates from the Rum Layered Intrusion showsvariable approach to sub-solidus textural equilibrium from aninitial state inherited by pseudmorphing of the last melt. Texturalequilibration at pore corners occurs as a continuous process,with a gradual movement of the entire dihedral angle populationtowards the equilibrium final state. If the initial, pseudomorphedstate is one of disequilibrium (i.e. a melt-present impingementtexture) this change is accompanied by a reduction in the spreadof the population. If it is one of equilibrium, the change isaccompanied by an initial increase in the spread of the population,followed by a decrease. These observations demonstrate thatpreviously published models of dihedral angle change involvingthe instantaneous establishment of the equilibrium angle inthe immediate vicinity of the pore corner are incorrect. KEY WORDS: cumulate; dihedral angle; textural evolution; Rum intrusion; Kula; Santorini  相似文献   

New Results at Mayon,Philippines, from a Joint Inversion of Gravity and Deformation Measurements     

K. F.?TiampoEmail author  J.?Fernández  G.?Jentzsch  M.?Charco  J. B.?Rundle 《Pure and Applied Geophysics》2004,161(7):1433-1452

In this paper, we detail the combination of the genetic algorithm (GA) inversion technique with the elastic-gravitational model originally developed by Rundle and subsequently refined by Fernández and others. A sensitivity analysis is performed for the joint inversion of deformation and gravity to each of the model parameters, illustrating the importance of proper identification of both the strengths and limitations of any source model inversion, and this technique in particular. There is a practical comparison of the theoretical results with the inversion of geodetic data observed at the Mayon volcano in the Philippines, where there are gravity changes without significant deformation, after the 1993 eruption.  相似文献   

Evolution of the north-polar cap of Mars: a modelling study     

Ralf Greve  Rupali A Mahajan  Björn Grieger 《Planetary and Space Science》2004,52(9):775-787

Celestial-mechanical computations show that, even stronger than for Earth, Mars is subject to Milankovi? cycles, that is, quasi-periodic variations of the orbital parameters obliquity, eccentricity and precession. Consequently, solar insolation varies on time-scales of 10⁴-10⁵ years. It has long been supposed that this entails climatic cycles like the terrestrial glacial-interglacial cycles. This hypothesis is supported by the light-dark layered deposits of the north- and south-polar caps indicating a strongly varying dust content of the ice due to varying climate conditions in the past. This study aims at simulating the dynamic and thermodynamic evolution of the north-polar cap (NPC) of Mars with the ice-sheet model SICOPOLIS. The boundary conditions of surface accumulation, ablation and temperature are derived directly from the solar-insolation history by applying the newly developed model MAIC. We consider steady-state scenarios under present climate conditions as well as transient scenarios over climatic cycles. It is found that the NPC is most likely not in steady state with the present climate. The topography of the NPC is mainly controlled by the history of the surface mass balance. Ice flow, which is of the order of , plays only a minor role. In order to build up the present cap during the last five million years of relatively low obliquities, a present accumulation rate of water equiv a⁻¹ is required. Computed basal temperatures are far below pressure melting for all simulations and all times.  相似文献   

A Generalized Representation of the Electromagnetic Fields In A Layered Earth     

David E. Boerner  G. F. West 《Geophysical Journal International》1989,97(3):529-547

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P-T-X (CO₂) conditions in mafic and calc-silicate hornfelses from Oberon, New South Wales, Australia     

A. S. ANDREW 《Journal of Metamorphic Geology》1984,2(2):143-163

Abstract The Rockley Volcanics from near Oberon, New South Wales occur within the aureole of the Carboniferous Bathurst Batholith and have been contact metamorphosed at P ∼ 100 ± 50MPa (10.5kbar) and a maximum T ∼ 565°C in the presence of a C–O–H fluid. Prior to contact metamorphism the volcanics were regionally metamorphosed and altered with the extensive development of actinolite, chlorite, plagioclase, quartz and calcite. The contact metamorphosed equivalents of these rocks have been subdivided into: Ca-poor (cordierite + gedrite), Mg-rich (amphibole + olivine + spinel), mafic (amphibole + plagioclase) and Ca-rich (amphibole + garnet + diopside; diopside + plagioclase; garnet + diopside + wollastonite) rocks.
The chemistry of the minerals in the hornfelses was controlled by the bulk rock chemistry and fluid composition. Pargasites and hastingsites as well as an unusual phlogopite with blue green pleochroism, are found in Ca-rich hornfelses. A comparison of the assemblages with experimentally derived equilibria suggests that the fluid phase associated with the Ca-rich hornfelses was water-rich (X_co2= 0.1 to 0.3) while that associated with the Mg-rich hornfelses was enriched in CO₂ (X_co2 > 0.7). The different hornfels types have reacted to contact metamorphism independently in both their solid and fluid chemistries.  相似文献   

An operational two-layer remote sensing model to estimate surface flux in regional scale: Physical background     

ZHANG Renhua  SUN Xiaomin  WANG Weimin  Xu Jinping  ZHU Zhilin  TIAN Jing 《中国科学D辑(英文版)》2005,48(Z1)

Based on the improved interaction mechanism of two-layer model, this paper proposed Pixel Component Arranging and Comparing Algorithm (PCACA) and theoretically positioning algorithm, estimated the true temperature of mixed pixel in four extreme points in combination with the measurements of dry and wet points in calibration fields and improved the reliability of positioning dry and wet line. A new two-layer energy-separation algorithm was proposed,which was simple and direct without resistance network parameters for each pixel. We also proposed a new thought about the effect of advection. The albedo of mixed pixel was also separated with PCACA. In combination with two-layer energy-separation algorithm, the net radiation of mixed pixel was separated to overcome the uncertainty of conventional energy-separation algorithm using Beer's Law. Through the validation of retrieval result, this method is proved to be feasible and operational. At the same time, the uncertainty of this algorithm was objectively analyzed.  相似文献   

Geochemistry of adakitic quartz diorite in the Yamizo Mountains, central Japan: Implications for Early Cretaceous adakitic magmatism in the inner zone of southwest Japan     

Yutaka  Takahashi  Shin-Ichi  Kagashima  Masumi U.  Mikoshiba 《Island Arc》2005,14(2):150-164

Abstract   Small-volume plutons of Early to Late Cretaceous ages are widely distributed in the Yamizo Mountains, central Japan. These plutons consist predominantly of granitoids, classified into hornblende gabbro, quartz diorite, hornblende–biotite granodiorite and coarse-grained biotite granite. The quartz diorite (52–64 wt% of SiO₂) is characterized by a high Sr content (606–769 p.p.m.) associated with a low Y (13–27 p.p.m.) and heavy rare earth element content (Yb content of 1.19–2.13 p.p.m.). On the Sr/Y versus Y diagram, this rock type mainly plots in the adakite and Archean high-Al tonalite, trondhjemite and granodiorite (TTG) field. Together with its initial Sr isotopic ratios, which range from 0.7038 to 0.7046, these data suggest that quartz diorite originated as slab melts. However, geochemical calculations assuming either eclogite or garnet amphibolite as the source material do not support this suggestion. Instead, the chemical compositions of quartz diorite are better explained by the fractional crystallization of hornblende, plagioclase and biotite from a primitive, basaltic melt in a magma chamber. In this case, the formation of the associated hornblende gabbro can also be explained by the accumulation of hornblende and plagioclase. Adakitic rocks of Early Cretaceous ages have also been reported in the Tamba Belt of the inner zone of southwest Japan, located ca 500 km west of the Yamizo Mountains. These rocks can be correlated to the adakitic rocks in the Yamizo Mountains based on the geology, petrography, geochemistry and radiometric ages. Therefore, we propose the possibility that the Early Cretaceous adakitic rocks in the inner zone of southwest Japan were produced by fractional crystallization from basaltic arc magmas generated by a partial melting of metasomatized wedge mantle peridotite.  相似文献   

Nb/Ta variations of mafic volcanics on the Archean- Proterozoic boundary: Implications for the Nb/Ta imbalance     

LIU Yongsheng    GAO Shan    WANG Xuance  HU Shenghong & WANG Jianqi . State Key Laboratory of Geological Processes  Mineral Resources  China University of Geosciences  Wuhan  China  . Key Laboratory of Continental Dynamics  Department of Geology  Northwest University  Xi’an  China 《中国科学D辑(英文版)》2005,48(8):1106-1119

Hofmann[1] found that the depleted mantle (DM) and bulk continental crust (BCC) are simply compen-satory in terms of many elements and elemental ratios. High-field-strength elements (HFSE) (e.g., Zr, Hf, Nb, Ta and Ti) are immobile and thus useful to track the primary features of the ancient mafic volcanics. It has been long considered that Nb-Ta behave as identical twins during magmatic processes, based on their matching atomic radii and valence state and hence coherent geochemical affi…  相似文献